Objective To investigate and analyze the morbidity of military personnel stationed on an island-reef from Jun. 2018 to Oct. 2019, and to provide basis for medical and health support. Methods The outpatient registration information was extracted from the island-reef hospital. The medical records were classified according to ICD-10 and related catalog, and the causes of diseases were analyzed combined with relevant data. Results A total of 15 601 cases were collected in this study. The top five common diseases on the reef hospital included orthopedic diseases (3 140 cases), skin diseases (3 017 cases), oral diseases (2 623 cases), respiratory diseases (1 451 cases) and otorhinolaryngologic diseases (1 228 cases), and some of them such as stomatology, respiratory system diseases and other common diseases were significantly related to the season. The proportions of oral and respiratory diseases in July were 20.41% (361/1 769) and 15.49% (274/1 769), respectively, which were higher than other time of the year. The prevalence of systemic diseases in different age groups was different. Compared with those under the age of 50, the percentages of diseases of general medicine (mainly in rheumatism, blood, kidney and endocrine diseases) and cardiology significantly increased in patients older than 50 years old, being 10.00% (10/180) and 5.56% (18/180), respectively (P<0.05). Conclusion The morbidity of military personnel stationed on the island-reef has obvious epidemiological characteristics, with different disease spectra in different age groups, and the medical support should be given with pertinence.